BUG/MEDIUM: session: Remove the session from the session_list in session_free.

When freeing the session, we may fail to free the outgoing connection,
because it still has streams attached. So remove ourself from the session
list, so that the connection doesn't try to access it later.

src/session.c

@@ -88,6 +88,7 @@ void session_free(struct session *sess)
 		conn_full_close(conn);
 		conn_free(conn);
 	}
+	LIST_DEL(&sess->conn_list);
 	pool_free(pool_head_session, sess);
 	HA_ATOMIC_SUB(&jobs, 1);
 }